Presently, the usage of radio spectrum is liberalized in that frequency bands are sometimes not exclusively assigned to one particular transmission system or in that frequency bands are sometime only assigned to one particular transmission system for a limited period of time. A reason for this is that frequency bands, assigned by licenses to licensees, are often not used during certain periods. For example, one possible approach pursued in regulations is to license the frequency band, or spectrum resource, to a licensee (primary user), while at the same time allow other users, or secondary users, to use the frequency band under the condition that the secondary users do not cause harmful interference to the system operation of the primary user. In future, there will be multitude of spectrum usage regimes applied for different portions of the electro-magnetic spectrum.
A first example of such a usage regime, or spectrum resource usage regime, is dedicated licensed spectrum operation, in which the licensee receives an exclusive license for using a certain spectrum portion, or frequency band, for a certain period of time in a certain region (e.g. 2G/3G cellular communication systems of today).
Further, a second regime is licensed spectrum operation with opportunistic spectrum access by secondary users, in which the primary user receives a non-exclusive license for using a certain spectrum portion for a certain period of time in a certain region, while other systems are allowed to use the licensed spectrum under a secondary license and/or under certain usage rules. For example, the other systems (secondary users) need to sense or detect if the licensee (primary user) is using the spectrum and if primary usage is detected, the secondary user has to withhold from or cease spectrum usage if the interference caused from the secondary system to the primary system exceeds a certain threshold (e.g. secondary usage of white space spectrum in US TV bands, as developed in IEEE 802.22).
Moreover, a third regime is licensed spectrum operation with allowance for spectrum trading, in which the licensee receives an exclusive license for using a certain spectrum portion for a certain period of time in a certain region with the option for renting out the usage of the licensed spectrum in exclusive secondary licenses. For example, a primary licensee has the spectrum usage right for a certain spectrum portion in a specific region for 20 years, but is only using the spectrum at certain time periods. The primary user can then lease the temporal/regional usage of the spectrum resources to secondary users on, for example, a yearly or monthly basis, or only during daily time periods, for example, during night.
In addition, as a variety of the third regime, an exclusive license for using a certain spectrum portion for a certain period of time in a certain region may be provided directly by a spectrum usage regulatory body for providing spectrum licenses, which would correspond to the primary user in the example above.
Furthermore, a fourth regime is un-licensed spectrum operation, in which the usage of a certain spectrum portion in a certain region is allowed to any system which fulfils certain usage policies, such as maximum allowed transmission power or sharing rules.
In an ad-hoc network, the network does not have an infrastructure. An exemplifying ad hoc network comprises a plurality of mobile stations, which may leave or attach to the network at will. Also, in this ad-hoc network there is a need for admission control. In order to perform admission control, one of the mobile stations needs to be configured as an admission control resource management node, a so called super node of the cluster of mobile terminals forming the ad-hoc network. Notably, admission control is hence performed in one of the mobile terminals. Alternatively, admission control may be performed in each mobile terminal.
With the independence of spectrum usage from specific service types (e.g. broadcasting, cellular communication services), it is possible for telecommunication systems to combine the usage of a multitude of spectrum portions, as long as the corresponding spectrum usage regime for each spectrum portion is applied. In such a system, a spectrum resource aggregation function of a mobile network performs aggregation of different spectrum resources and performs common resource management for these resources. One spectrum resource can, for example, be the licensed spectrum of the operator of the mobile network with exclusive usage right according to a dedicated licensed spectrum operation, another spectrum resource can be licensed with a temporarily exclusive usage right according to a secondary license that was bought from another mobile network operator or TV broadcast operator, a third spectrum resource may be non-exclusively licensed by another system (e.g. a TV broadcast operator or a radar system) which is used by the mobile network opportunistically, and a fourth spectrum resource may be an unlicensed spectrum resource that is used by an unknown amount of systems.
Throughout the disclosure of this application, the term “spectrum-on-demand system” shall be understood as comprising a mobile network system, which makes use of spectrum resources that are not assigned to the mobile network operator under a primary exclusive license, possibly but not necessarily, in addition to any primary spectrum resources.
In a spectrum-on-demand system, the resources comprising the different resource components provided by the individual spectrum resources are managed by a common resources management unit or center. This does not exclude that further resource management functions are performed within each system resource, like for example, power control, congestion control and more. This common resource management unit includes functions like admission control of services and service allocation.
Admission control is part of most communication networks. The basic functionality of admission control is to allow as many services into the system as can be supported by the spectrum resources such that the minimum service requirements are still met. If all resources are occupied, any further service requests will be rejected. The following condition needs to be fulfilled at all times:
                                                                        ∑                j                            ⁢                              s                j                                      ≤                          A              t                                =                                    C              tot                        -                          A              m                                      ,                            (        1        )            where sj is the amount of resources required for serving a session j, At is the admission threshold denoting the maximum amount of occupied resources before admission control rejects the admittance of new services, Ctot is the total capacity of resources managed by the admission control and Am is an admission control margin. The admission control threshold compensates that the amount of resources required for a service sj is not constant, as it may change e.g. with fluctuations of the radio channel due to mobility, fading or varying interference, or user mobility. An admission control margin, Am balances this uncertainty/estimation error. In addition, the admission control margin, Am can be used to account for fractional loading requirements, i.e., when a given gross capacity cannot be loaded to 100% due to Quality of Service (QoS) requirements of the carried traffic. The total capacity Ctot depends on the resources that are allocated to the system. In mobile networks, total capacity is capacity of the spectrum resource allocated to the used access technology. Mobile networks may also combine a multitude of spectrum resources. This is, for example, the case when a mobile network operator has different spectrum licenses for different spectrum portions and uses the same access technology on multiple carriers. As a further example, a mobile network operator may have different spectrum licenses for different spectrum portions, in which it operates different access technologies like a GSM/EDGE Radio Access Network in the GSM frequency band, a UMTS Radio Access Network in the UMTS frequency band, and a LTE Radio Access Network in new IMT frequency bands. As shown in FIG. 2, the total capacity that is used for admission control in such a system with multiple spectrum resources is determined as the sum of the capacities of the different spectrum resources.
Using this common admission control approach for multiple spectrum resources in a spectrum-on-demand system may cause service degradation or inefficient utilization of spectrum resources. Hence, there is a need for an improved procedure for determining the admission control threshold.